Variable back pressure check valve and drain valve

ABSTRACT

A fluid receiver is connected via a supply orifice to a pressurized fluid supply source and via a fluid drain orifice to a relatively low pressure fluid drain source. A fluid pressure responsive spring-loaded check valve connected to the supply orifice and a drain valve connected to the drain orifice are provided with a one way collapsible link including a compression spring connecting the same causing the drain valve to open when the check valve is fully closed and close in response to compression of the spring when the check valve moves a predetermined distance in an opening direction. The check valve is provided with a contoured end portion and parallel flow passages in series flow therewith. One of the parallel flow passages includes a venturi for generating a fluid pressure which varies as a function of the flow therethrough and which is imposed on the check valve to assist the spring force acting thereagainst.

United States Patent [151 3,665,950 Nelson [451 May so, 1972 [54]VARIABLE BACK PRESSURE CHECK Primary ExaminerSamuel B. Rothberg VALVEAND DRAIN VALVE Assistant Examiner-William H. Wright Attorney-Gordon H.Chenez and Plante, Hartz, Smith and [72] Inventor: Thomas A. Nelson,South Bend, lnd. Th [73] Assignee: The Bendix Corporation ABSTRACT 22 F!d: I 13 1970 I I '6 y A fluid receiver is connected via a supply orificeto a pres- [2l] Appl. No.: 54,416 surized fluid supply source and via afluid drain orifice to a relatively low pressure fluid drain source. Afluid pressure 52] U S Cl 137/107 137/1 137 l 6 3 responsivespring-loaded check valve connected to the supply [51] F1 11/22 i=02h55/60 orifice and a drain valve connected to the drain orifice are [58]i 102 3 l 16 provided with a one way collapsible link including acompression spring connecting the same causing the drain valve to openwhen the check valve is fully closed and close in [56] References cuedresponse to compression of the spring when the check valve UNITED STATESPATENTS moves a predetermined distance in an opening direction. Thecheck valve is provided with a contoured end portion and 2,969,8061/[961 Jensen ..l37/l07 parall l flow passages in series flow therewith,One of the 3,102,549 3 flparallel flow passages includes a venturi forgenerating a fluid Bueler pressure varies as a function of the flowtherethrough Swedberg and is imposed on the check valve to assist thepring force acting thereagainst.

9 Claims, 2 Drawing Figures w 20 1 W 4. A I 90 H0 /0 M I36 w 13 9METERED i Q ,l -/22 26 FUEL AT 74 i I I/ 46 Pnss 1, 120 p 1 /30 DRAIN r76 2 4 ma our 1 2 0 68 l0 1%, 8 3 e 2 I 8 ll 8 1 k w66 l06fl\ j l I y l//4 ll 86 A //8 H6 //2 L 58 09 I 36 I 30 w 6 1 E a p l 26 l 26 m FUEL #1Po A METER 8 Q ll EL-Z E ,4 FUEL 24. .92 SOURCE Patented May 30, 1972METERED FUEL AT PRESS FUiL OUT 7 26 pm I F h 1- E3 4 -24 7.] 056. //v9/[1 40 24 '32 FUEL SOURCE I N VEN '1 '(JR. THO/V145 A. NELSON AGENTVARIABLE BACK PRESSURE CHECK VALVE AND DRAIN VALVE BACKGROUND OF THEINVENTION This invention pertains to a combination check and drain valveparticularly of the type utilized in controlling pressurized fuel flowto and draining of fuel from a' fuel manifold of a combustion engine.

The conventional combustion engine fuel system may include a fuelpressure responsive check valve adapted to restrict flow of fuel to afuel manifold downstream therefrom until a predetermined fuel pressureis reached at which time the check valve opens to pressurize the fuelmanifold with fuel. The fuel pressure at which the check valve opens isnormally determined by a predetermined fixed spring load imposed againstthe check valve to urge the same closed which, in turn, requires apredetermined fuel pressure drop across the check valve to hold the sameopen. Once open, the check valve is incapable of exercising anyreasonably significant controlover the flow of fuel therethrough to thefuel nozzles which control, in certain engine fuel control systems, maybe desirable. Furthermore, in the case of aircraft, engine fuelrequirements normally vary over a wide range with the fuel requirementdecreasing with increasing flight altitude as will be recognized bythose persons skilled in the art. At low fuel flows, the check valve maybe subject to unstable operation in that the force tending to hold thevalve open may not greatly exceed the opposing spring force tending toclose the check valve.

SUMMARY OF THE INVENTION The present invention provides fluid flowcontrol means having a check valve portion for venting pressurized fluidflow to a receiver and a drain valve portion for venting the receiver toa relatively lower pressure fluid source. The check valve portion isresiliently loaded to a closed seated portion and is provided with afluid pressure responsive member responsive to a variable control fluidpressure derived from the fluid pressure drop across the check valve asthe check valve moves in an opening direction. At high fluid flows, thecheck valve is actuated to a fully open position thereby presentinglittle restriction to fluid flow therethrough. At relatively lower fluidflows, the check valve moves toward a closed position whereuponacontoured portion thereof becomes effective to establish a variableeffective flow area which decreases to restrict flow therethroughaccordingly. When the fluid pressure upstream from the check valve dropsto a predetermined value, the check valve moves to a closed positionthereby allowing the drain valve to open and vent the receiver to thelower pressure fluid source.

It is an object of the present invention to provide a fluid flow checkvalve and control means for generating a variable force loading againstthe check valve to vary the efiective flow therethrough.

It is another object of the present invention to provide a compact andreliable combination check valve and drain valve.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates a sectionalschematic view of the present invention as embodied in a conventionalfuel system for a gas turbine engine.

FIG. 2 is a curve showing the relationship between metered fuel flow,W,, at pressure P, and the fuel pressure differential, P P betweenmetered fuel and the combustion chamber fuel nozzle fuel pressure, P

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing,numeral 20 designates the present invention shown in combination with aconventional gas turbine engine 22 fuel system generally indicated by24. The fuel system 24 includes a fuel supply conduit 26 connecting afuel tank 28 with an annular fuel manifold 30 mounted on engine 22. Anengine driven fuel pump 32 and fuel meter 34 downstream therefrom aredisposed in conduit 26 and serve to generate a controlled flow ofpressurized fuel through conduit 26 to fuel manifold 30 from which thepressurized fuel is injected via a plurality of fuel nozzles 36 toassociated combustion chambers 38. The controlled flow may vary as afunction of one or more variable conditions of engine operation such asengine speed and the position of an engine power output control lever 40suitably connected to fuel meter 34.

As pointed out heretofore, the rate of fuel flow to manifold 30 shouldbe maintained above a predetermined minimum value to establishsatisfactory fuel pressurization of manifold 30 and thus pressuredifferential across fuel nozzles 36 depending upon the range ofcombustion chamber gas pressure to which the fuel nozzles discharge overthe operating range of the engine. To that end, applicant's check anddrain valve 20 is disposed in conduit 26 downstream from fuel meter 34and serves to block fuel flow to fuel manifold 30 as necessary toprevent inadequate pressurization of manifold 30 as well as drain fuelfrom manifold 30 under engine shut down condi tions in a manner to bedescribed.

The check and drain valve 20 includes a casing 42 having an inlet port44 and an outlet port 46 in series flow relationship with conduit 26. Adrain port 48 in casing 42 is connected via a passage 50 to fuel conduit26 at relatively low fuel pump inlet pressure P upstream from fuel pump32. The inlet port 44 is defined by a sleeve member 52 slidably receivedby a bore 54in casing 42 and provided with a flanged portion 56. Aplurality of screws 58 extend through flanged portion 56 into threadedengagement with casing 42 to removably secure sleeve member 52 inposition in casing 42. The sleeve member 52 is provided with a'reduceddiameter section defining a valve seat 60 and is suitably recessed toreceive an 0" ring seal 62 to prevent fuel leakage between adjacentsurfaces of sleeve member 52 and casing 42.

A check valve member 42 slidably carried in bore 54 is provided with alongitudinal bore 66 reduced in diameter at one end thereof to formspaced-apart shoulders 68 and 70. A plug 72 slidably received by bore 66bears against shoulder 68 and is fixed in position rotationally relativethereto by a locating pin 74 suitably retained by shoulder 68 and plug72. The plug 72 is secured in position by a screw member 76 threadedlyengaged with plug 72 and adapted to bear against shoulder 70.

A bevelled end portion 78 formed on check valve member 64 is separatedfrom a bevelled portion 80 by a land 82 which is slidably received bythe reduced diameter section of sleeve member 52 to permit bevelledportion 80 to engage valve seat 60 under the influence of a compressionspring 84 interposed between check valve member and casing 42. Anannular chamber 86 partially defined by a skirt portion 88 of checkvalve member 64 is adapted to receive fuel from inlet port 44 andcommunicate with outlet port 46 via a plurality of circ umferentiallyspaced-apart openings 90 in skirt portion 88 as will be described. Theannular chamber 86 further communicates with outlet port 46 viadiametrically opposed passages 92 and 94 in check valve member 64 and anorifice or venturi 96 suitably secured in plug 72 and connectingpassages 92 and 94. Venturi 96 throat pressure P. is vented viaassociated radial passages 98 and annulus 100 to an axial passage 102and radial passages 104 formed in a reduced diameter portion 106 of plug72 which radial passages 104 communicate with a chamber 108 partiallydefined by plug 72 and check valve member 64. One or-more restrictedpassages 109 in check valve member 64 and in parallel flow relationshipwith venturi 96 connects recess 86 with outlet 46.

The drain port 48 is defined by a sleeve member 110 suitably secured incasing 42 as by a press fit and an annular valve seat 112 formedthereon. The sleeve member 110 is suitably recessed to accommodate an Oring seal 114 to establish a fluid seal between adjacent surfaces ofcasing 42 and sleeve member 110. A drain valve 116 slidably carried bycasing 42 is suitably recessed to accommodate an 0 ring seal 118 toestablish a fluid seal between adjacent surfaces of casing 42 and drainvalve 116. One end of drain valve 116 is recessed to accommodate anannular-shaped resilient seal 120 which is secured in position by aretainer 122 through which a lock screw 124 extends into threadedengagement with drain valve 116. The opposite end of drain valve 116 isprovided with an axially extending circular recess 126 having a radiallyinwardly extending shoulder 128 at the open end thereof. The recess 126is adapted to slidably receive an enlarged diameter portion or stop 130of a stem 132 integral with plug 72. A compression spring 134 interposedbetween retaining shoulders 136 and 138 formed on plug 72 and drainvalve 116, respectively, serves to urge the same apart causing stopportion 130 to engage shoulder 128 as shown in the drawing therebyholding drain valve 116 in its open position which, in turn, vents drainport 48 to a passage 140 leading from outlet port 46.

OPERATION OF THE PREFERRED EMBODIMENT Assuming the control lever 40 tobe in a fuel cut-off position, fuel meter 34 will block fuel flowthrough conduit 26 thereby rendering the engine 22 inoperative. Undersuch a condition, it is desirable to vent the manifold 30 to arelatively low pressure fuel source to drain the fuel manifold and avoidundesirable fuel dribble through the fuel nozzles 36 into combustionchambers 38. To that end, the check valve 72 and drain valve 116 areurged to the positions shown in FIG. 1 by the compression spring 84which seats valve 72 against seat 60 and compression spring 134 whichurges drain valve 116 away from check valve 72 causing shoulder 128 toengage stop 130. It will be noted that the stop 130 prevents drain valve116 from closing thereby venting the manifold 30 to drain fuel pressureP, to drain fuel from manifold 30.

Now, assuming the control-lever 40 to be actuated to a positionrequesting engine operation at a maximum power output, the fuel meter 34establishes a corresponding flow of pressurized fuel at pressure P,,,through conduit 26 to inlet 44. The fuel at pressure P acts againstclosed valve member 64 in opposition to the force of spring 84 plus theforce of relatively low drain fuel pressure P in chamber 108 derivedfrom the throat of venturi 96. The resulting force unbalance urges checkvalve 72 in an opening direction thereby unseating the same from valveseat 60. The land 82 is sized to provide a relatively loose sliding fitthereof with casing 42 such that unseating valve 72 permits fuel to passthrough the annular clearance defined by land 82 into recess 86 fromwhich the fuel flows through restricted passages 109 and venturi 96 tooutlet 46. The effective flow areas of venturi 96 and passages 109 arerelatively large compared to that of the annular clearance defined byland 82 and adjacent casing 42 such that the major restriction to fuelflow and thus pressure differential between inlet 44 and outlet 46occurs at the land 82.

Since the drain valve 116 is held fixed in position relative to valvemember 64 by spring 134, the drain valve 116 moves toward seat 112. Asbevelled end portion 78 moves axially into alignment with valve seat 60,the drain valve 116 moves into engagement with seat 112 which compressesresilient seal 120 to a predetermined extent thereby establishing apositive seal against flow from passage 140 to passage 50 at pressureP,,. The valve member 64 continues to move under the influence ofpressure P, thereby defining a progressively increasing annular flowarea by virtue of the decreasing effective diameter of bevelled endportion 78 which, in turn, results in increased fuel flow to recess 86.As the effective flow area defined by bevelled end portion 78 increases,the venturi 96 senses the fuel flow from inlet 44 to outlet 46 with theresulting throat pressure P, generated at venturi 96 varyingsubstantially as a function of the pressure drop from inlet 44 to outlet46. The resulting throat pressure of venturi 96 increases but at alesser rate than the downstream pressure P and is transmitted to chamber108 where the increased force derived therefrom tends to oppose openingmovement of valve 64 which, in turn, presents increased resistance tofuel flow through check valve 64 and thus a corresponding increasedpressure drop between inlet 44 and outlet 46. However, it will beunderstood that the pressure drop between inlet 44 and outlet 46although increasing is still significantly less at any given fuel flowrate than would occur if the venturi 96 was not present. The smalldiameter end of bevelled portion 78 moves into radial alignment with theadjacent edge of seat 60 at which position of valve 64 the openings ofskirt portion 88 begin to register with outlet 46. As the effective areaof openings 90 increases thereby venting fuel to outlet 46 in parallelto that through venturi 96, the pressure drop between inlet 44 andoutlet 46 for a given fuel flow rate varies substantially linearly asshown in the curve of FIG. 2. It will be noted from FIG. 2 that theopenings 90 become effective at a predetermined fuel flow rate abovewhich the pressure drop vs fuel flow rate relationship is linear andbelow which the pressure drop vs fuel flow rate relationship is a squarefunction.

Upon movement of check valve 64 to a position establishing maximum flowarea of openings 90, a maximum fuel flow rate is establishedcorresponding to the desired maximum power output of the engine.

It will be recognized that a reversal in the above-described fuel flowrate trend, i.e., in a decreasing direction from maximum, will result ina like predetermined pressure drop between inlet 44 and outlet 46 foreach fuel flow rate as indicated in FIG. 2.

The variable back pressure against fuel flow established by check valve64 is particularly useful in providing a fuel flow derichment effect onthe fuel meter 34. To that end, the variable back pressure imposed onmetered fuel pressure at P by the check valve 64 may be sensed bysuitable conventional fuel pressure sensitive apparatus, not shown, inthe fuel meter 34 to generate a corresponding reduction in the fuel flowrate established by fuel meter 34. Such a fuel flow derichment effectmay be desirable in providing a fuel flow decrease as a function ofincreasing flight altitude.

I claim:

1. A variable back pressure fluid flow check valve comprising:

a casing having an inlet connected to receive pressurized fluid at avariable flow rate and an outlet connected to a fluid receiver;

check valve means operatively connected to said inlet and outlet forcontrolling the effective flow area therebetween and thus the fluidpressure drop therebetween;

resilient means operatively connected to said valve means for imposing apredetermined force preload thereon tending to close the same inopposition to force derived from said pressurized fluid acting againstsaid valve means;

fluid flow responsive means operatively connected in series flowrelationship with said inlet and outlet for generating a control fluidpressure which varies as a function of the fluid pressure drop betweensaid inlet and outlet; and

force producing means responsive to said control fluid pressureoperatively connected to said valve means for imposing a force thereonto augment said resilient means.

2. A variable back pressure fluid flow check valve as claimed in claim 1and further including:

a drain port in said casing connected to a relatively low pressure fluiddrain source;

normally closed drain valve means operatively connected to said outletand said drain port for establishing and disestablishing fluidcommunication therebetween; and

means operatively connecting said check valve means and said drain valvemeans for actuating said drain valve means to an open position inresponse to movement of said check valve means to a closed position andto a closed position in response to movement of said check valve meansto an open position.

3. A variable back pressure fluid flow check valve as claimed in claim 1wherein:

said check valve means is slidably carried in said casing and providedwith first and second valve portions operative with said inlet andoutlet, respectively, to define corresponding first and second variableflow areas;

conduit means including said fluid flow responsive means in series flowrelationship with said first valve portion and in parallel flowrelationship with said second valve portion;

said-check valve means being operative over a first range of positionswherein said first valve portion is open and said second valve portionis closed with the resulting fluid flow through said inlet passingthrough said conduit means to said outlet and a second range ofpositions wherein said first valve portion is open and said second valveportion is open with the resulting fluid flow through said inlet passingthrough said second valve portion and said conduit means to said outlet.

4. A variable back pressure fluid flow check valve as claimed in claim 1wherein:

said inlet defines an annular valve seat;

said check valve means is slidably carried in said housing and providedwith a contoured end having a portion thereof adapted to seat on saidvalve seat to block said inlet;

a chamber formed in said housing downstream from said inlet;

a skirt formed on said check valve means and provided with a pluralityof openings therein communicating with said chamber and adapted toregister with said outlet to a varying degree depending upon theposition of said check valve means;

a passage in said check valve means connecting said chamber with saidoutlet in parallel to said plurality of openings;

said fluid flow responsive means being disposed in said passage meansand responsive to fluid flow therethrough;

said check valve means being actuable off said valve seat and having afirst range of positions wherein said contoured end portion establishesa variable effective flow area of said inlet with said plurality ofopenings blocked and a second range of positions wherein said pluralityof openings register with said outlet to vent fluid from said chamber tosaid outlet in parallel with fluid flow through said passage.

5. A variable back pressure fluid flow check valve as claimed in claim 4wherein:

said resilient means is a compression spring urging said check valvemeans into seating engagement with said valve seat; and said forceproducing means being defined by a predetermined effective area of saidcheck valve means exposed to said control fluid pressure for generatinga variable force augmenting said compression spring. 6. A variable backpressure fluid flow check valve as claimed in claim 2 wherein:

said means operatively connecting said check valve means includes a stopmember fixedly secured to said check valve means and movable therewith;said drain valve means being slidably carried on said check valve meansand engageable with said stop member to limit the movement of said drainvalve means relative to said check valve means; and a compression springinterposed between said check valve means and said drain valve means forurging said drain valve means into engagement with said stop member. 7.-A variable back pressure fluid flow check valve as claimed in claim 2wherein:

said pressurized fluid is a controlled flow of fuel for a combustionengine; said fluid receiver is a fuel manifold connected to supply saidfuel to combustion chambers of the combustion engine; and saidrelatively low pressure fluid drain source is a source of fuel. 8. Avariable back pressure fluid flow valve as claimed in claim 6 wherein:

said inlet and said drain port are arranged in spaced apart co-axialrelationship; said check valve means and said drain valve means arearranged in spaced apart coaxial relationship and interposed betweensaid inlet and said drain port in axial alignment therewith. 9. Avariable back pressure fluid flow check valve as claimed in claim 3wherein:

said fluid flow responsive means is a venturi wherein said control fluidpressure generated thereby varies as a function of fluid flowtherethrough and thus the fluid pressure drop thereacross.

1. A variablE back pressure fluid flow check valve comprising: a casinghaving an inlet connected to receive pressurized fluid at a variableflow rate and an outlet connected to a fluid receiver; check valve meansoperatively connected to said inlet and outlet for controlling theeffective flow area therebetween and thus the fluid pressure droptherebetween; resilient means operatively connected to said valve meansfor imposing a predetermined force preload thereon tending to close thesame in opposition to force derived from said pressurized fluid actingagainst said valve means; fluid flow responsive means operativelyconnected in series flow relationship with said inlet and outlet forgenerating a control fluid pressure which varies as a function of thefluid pressure drop between said inlet and outlet; and force producingmeans responsive to said control fluid pressure operatively connected tosaid valve means for imposing a force thereon to augment said resilientmeans.
 2. A variable back pressure fluid flow check valve as claimed inclaim 1 and further including: a drain port in said casing connected toa relatively low pressure fluid drain source; normally closed drainvalve means operatively connected to said outlet and said drain port forestablishing and disestablishing fluid communication therebetween; andmeans operatively connecting said check valve means and said drain valvemeans for actuating said drain valve means to an open position inresponse to movement of said check valve means to a closed position andto a closed position in response to movement of said check valve meansto an open position.
 3. A variable back pressure fluid flow check valveas claimed in claim 1 wherein: said check valve means is slidablycarried in said casing and provided with first and second valve portionsoperative with said inlet and outlet, respectively, to definecorresponding first and second variable flow areas; conduit meansincluding said fluid flow responsive means in series flow relationshipwith said first valve portion and in parallel flow relationship withsaid second valve portion; said check valve means being operative over afirst range of positions wherein said first valve portion is open andsaid second valve portion is closed with the resulting fluid flowthrough said inlet passing through said conduit means to said outlet anda second range of positions wherein said first valve portion is open andsaid second valve portion is open with the resulting fluid flow throughsaid inlet passing through said second valve portion and said conduitmeans to said outlet.
 4. A variable back pressure fluid flow check valveas claimed in claim 1 wherein: said inlet defines an annular valve seat;said check valve means is slidably carried in said housing and providedwith a contoured end having a portion thereof adapted to seat on saidvalve seat to block said inlet; a chamber formed in said housingdownstream from said inlet; a skirt formed on said check valve means andprovided with a plurality of openings therein communicating with saidchamber and adapted to register with said outlet to a varying degreedepending upon the position of said check valve means; a passage in saidcheck valve means connecting said chamber with said outlet in parallelto said plurality of openings; said fluid flow responsive means beingdisposed in said passage means and responsive to fluid flowtherethrough; said check valve means being actuable off said valve seatand having a first range of positions wherein said contoured end portionestablishes a variable effective flow area of said inlet with saidplurality of openings blocked and a second range of positions whereinsaid plurality of openings register with said outlet to vent fluid fromsaid chamber to said outlet in parallel with fluid flow through saidpassage.
 5. A variable back pressure fluid flow check valve as claimedin claim 4 wherein: said resilient means is a compression spring urgingsaid check valve means into seating engagement with said valve seat; andsaid force producing means being defined by a predetermined effectivearea of said check valve means exposed to said control fluid pressurefor generating a variable force augmenting said compression spring.
 6. Avariable back pressure fluid flow check valve as claimed in claim 2wherein: said means operatively connecting said check valve meansincludes a stop member fixedly secured to said check valve means andmovable therewith; said drain valve means being slidably carried on saidcheck valve means and engageable with said stop member to limit themovement of said drain valve means relative to said check valve means;and a compression spring interposed between said check valve means andsaid drain valve means for urging said drain valve means into engagementwith said stop member.
 7. A variable back pressure fluid flow checkvalve as claimed in claim 2 wherein: said pressurized fluid is acontrolled flow of fuel for a combustion engine; said fluid receiver isa fuel manifold connected to supply said fuel to combustion chambers ofthe combustion engine; and said relatively low pressure fluid drainsource is a source of fuel.
 8. A variable back pressure fluid flow valveas claimed in claim 6 wherein: said inlet and said drain port arearranged in spaced apart co-axial relationship; said check valve meansand said drain valve means are arranged in spaced apart coaxialrelationship and interposed between said inlet and said drain port inaxial alignment therewith.
 9. A variable back pressure fluid flow checkvalve as claimed in claim 3 wherein: said fluid flow responsive means isa venturi wherein said control fluid pressure generated thereby variesas a function of fluid flow therethrough and thus the fluid pressuredrop thereacross.